Constant oil control keeps bearings running

Anglo-Japanese roller bearings manufacturer, NSK-RHP, believes it has overcome one of the main problems for maintenance engineers who must keep continuous casting lines moving: premature bearing failure associated with grease or conventional oil-air lubrication methods.

The breakthrough lies in the ability to continuously monitor and control the pressure inside each roller bearing housing during casting. Continuous monitoring of the oil mist system enables engineers to detect abnormalities such as leaks from oil inlets or seals on bearing housings.

It has been proven under the onerous conditions of a continuous casting line, opening up a potentially wide range of applications.

The results of a two-year trial in Japan show the potential to double bearing life with the associated benefits of increased reliability of the casting line and lower operational costs. Since oil leaks can be monitored so precisely, the environment benefits too.

Bearing lubrication is always a key issue in maintaining production plant but the job becomes especially difficult in the harsh conditions characterised by high temperatures and very slow speeds of the casting line, and very heavy loads.

Because the bearings rotate so slowly it is difficult to maintain the hydro-dynamics that keep the lubricant flowing efficiently and prevent metal to metal contact.

Grease-lubricated bearings are particularly vulnerable to high temperature operation because of the failure of seals which lead to grease oils evaporating or leaking. Water, to cool the bearings, gets in and causes corrosion.

In the new system, which replaces grease or conventional oil-air systems, tight control of the oil-air supply and the pressure of the oil-air supply inside the bearing housing ensures the lubricant stays in contact with the bearings.

Positive pressure keeps out dirt. The air prevents friction on the bearing seal and, together with the entrained oil, provides oil bath cooling. Since oil never reaches the upper limit of the housing seal, none leaks to the environment.

The system uses only a tenth of the oil required for normal mist lubrication.